The typical hard disk drive includes a head disk assembly (HDA) and a printed circuit board (PCB) attached to a disk drive base of the HDA. The head disk assembly includes at least one disk, a spindle motor for rotating the disk, and a head stack assembly (HSA). The printed circuit board assembly includes electronics and firmware for controlling the rotation of the spindle motor and for controlling the position of the HSA, and for providing a data transfer channel between the disk drive and its host.
The spindle motor typically includes a rotor including one or more rotor magnets and a rotating hub on which disks mounted and clamped, and a stator. If more than one disk is mounted on the hub, the disks are typically separated by spacer rings that are mounted on the hub between the disks. Various coils of the stator are selectively energized to form an electromagnetic field that pulls/pushes on the rotor magnet(s), thereby rotating the hub. Rotation of the spindle motor hub results in rotation of the mounted disks.
The head stack assembly typically includes an actuator, at least one head gimbal assembly (HGA), and a flex cable assembly. During operation of the disk drive, the actuator must rotate to position the HGAs adjacent desired information tracks on the disk. The actuator includes a pivot-bearing cartridge to facilitate such rotational positioning. The pivot-bearing cartridge fits into a bore in the body of the actuator. One or more actuator arms extend from the actuator body. An actuator coil is supported by the actuator body, and is disposed opposite the actuator arms. The actuator coil is configured to interact with one or more fixed magnets in the HDA, typically a pair, to form a voice coil motor. The printed circuit board assembly provides and controls an electrical current that passes through the actuator coil and results in a torque being applied to the actuator.
Each HGA includes a head for reading and writing data from and to the disk. In magnetic recording applications, the head typically includes an air bearing slider and a magnetic transducer that comprises a writer and a read element. For example, FIG. 1 depicts a distal portion of a typical HGA 100 that includes magnetic recording head 102. Head 102 comprises air bearing slider 104 and magnetic transducer 106. The magnetic transducer's writer may be of a longitudinal or perpendicular design, and the read element of the magnetic transducer is typically magnetoresistive (MR). The head 102 is adhered to a gimbal 112 of a suspension assembly 110. Suspension assembly 110 also includes a load beam 114, a bend region (not shown), and a swage plate (not shown). The suspension assembly 110 acts to preload the air bearing slider against the surface of the disk. Electrical communication with the magnetic transducer is accomplished via gimbal traces 116, which are electrically connected to bond pads on the head by solder balls 120.
MR read elements of all types are easily damaged by electrostatic discharge (ESD), and tunneling MR read sensors (a.k.a. “TMR” read sensors) in particular are very easily damaged by ESD even at comparatively lower voltages. Prior art methods for protecting MR read sensors from damage due to ESD have had limited success for various reasons. For example, some prior art methods have undesirably and/or excessively complicated wafer-processing steps during manufacture of the magnetic recording heads. Other prior art methods offer insufficient ESD protection and/or do not afford protection early enough in the manufacturing process. For example, TMR read sensors are particularly vulnerable to ESD damage during the manufacturing process before the bond pads of the head are electrically connected to HGA gimbal traces (which may themselves connect to some protective circuitry). Thus, there is a need in the art for an improved method to fabricate a read transducer including a TMR read sensor.